The furnace heat exchanger is responsible for transferring heat from the combustion chamber to the air circulating throughout your home. Over time, the heat exchanger may become damaged or develop cracks, which can lead to a range of problems, including reduced efficiency, increased energy costs, and even safety hazards.

Here, we will discuss how to know when your furnace heat exchanger needs repair.

What Is a Furnace Heat Exchanger?

Before we delve into the signs of a damaged furnace heat exchanger, let us first understand what it is. A furnace heat exchanger is a component of your heating system that converts the heat generated during combustion into warm air that circulates throughout your home.

It is composed of a series of tubes or coils that are exposed to the heat produced by the burner. As the air passes over the tubes or coils, it absorbs the heat, which warms it up before being distributed through the ducts.

Signs of a Damaged Furnace Heat Exchanger

1. Increased Carbon Monoxide Levels

One of the most serious signs of a damaged furnace heat exchanger is increased carbon monoxide levels. A cracked or damaged heat exchanger can allow carbon monoxide, a toxic gas, to escape into your home. Carbon monoxide is odourless, colourless, and tasteless, making it impossible to detect without a carbon monoxide detector.

It may be a sign of carbon monoxide poisoning if you notice symptoms such as headaches, dizziness, nausea, or fatigue. In such cases, it is important to evacuate your home immediately and call a professional for furnace repairs.

2. Strange Noises

Another sign of a damaged furnace heat exchanger is strange noises from your heating system. A damaged heat exchanger can cause rattling, popping, or banging sounds, which are caused by the expansion and contraction of the metal as it heats up and cools down.

If you notice these types of noises, it is important to have your furnace inspected by a professional.

3. Reduced Efficiency

A damaged furnace heat exchanger can also result in reduced efficiency and increased energy costs. If your furnace is not heating your home as effectively as it used to, or if you notice a sudden increase in your energy bills, it may be a sign that your heat exchanger needs repairs.

A professional HVAC technician can inspect your furnace and identify the cause of the problem.

4. Visible Signs of Damage

In some cases, you may see visible signs of damage to your furnace heat exchanger. Cracks, rust, or corrosion on the heat exchanger can be a sign of damage.

If you notice any of these signs, it is important to have your furnace inspected by a professional as soon as possible.

5. Soot Accumulation

If you notice a soot buildup around your furnace, it may indicate a damaged heat exchanger. Soot buildup can occur when the heat exchanger is not functioning properly and cannot transfer heat efficiently. This can result in incomplete combustion, which produces soot.

If you notice soot buildup around your furnace, it is important to have it inspected by a professional.


Your furnace heat exchanger plays a critical role in the performance and safety of your heating system. If you notice any of the signs mentioned above, it is important to have your furnace inspected by a professional HVAC technician.

A damaged or cracked heat exchanger can lead to reduced efficiency, increased energy costs, and safety hazards such as carbon monoxide leaks. Regular maintenance and inspections can help prevent these problems and ensure your heating system functions safely and efficiently.

Trust 4 Seasons Home Comfort for all your furnace repair needs in Lethbridge. Our HVAC technicians are here to provide reliable and efficient furnace repair services to keep your home comfortable all winter long. Contact us today to schedule an appointment and ensure your furnace is in top condition.